JVET_M0064_CCLM_SIMPLIFICATION: replace calculations of CCLM parameter

  * Division table reduction
  * bit-width restriction

source/Lib/CommonLib/IntraPrediction.cpp

@@ -1784,6 +1784,37 @@ void IntraPrediction::xGetLMParameters(const PredictionUnit &pu, const Component
 
   if (leftAvailable || aboveAvailable)
   {
+#if JVET_M0064_CCLM_SIMPLIFICATION
+    int diff = maxLuma[0] - minLuma[0];
+    if (diff > 0)
+    {
+      int diffC = maxLuma[1] - minLuma[1];
+      int x = floorLog2( diff );
+      static const uint8_t DivSigTable[1 << 4] = {
+        // 4bit significands - 8 ( MSB is omitted )
+        0,  7,  6,  5,  5,  4,  4,  3,  3,  2,  2,  1,  1,  1,  1,  0
+      };
+      int normDiff = (diff << 4 >> x) & 15;
+      int v = DivSigTable[normDiff] | 8;
+      x += normDiff != 0;
+
+      int y = floorLog2( abs( diffC ) ) + 1;
+      int add = 1 << y >> 1;
+      a = (diffC * v + add) >> y;
+      iShift = 3 + x - y;
+      if ( iShift < 1 ) {
+        iShift = 1;
+        a = ( (a == 0)? 0: (a < 0)? -15 : 15 );   // a=Sign(a)*15
+      }
+      b = minLuma[1] - ((a * minLuma[0]) >> iShift);
+    }
+    else
+    {
+      a = 0;
+      b = minLuma[1];
+      iShift = 0;
+    }
+#else // original
     a         = 0;
     iShift    = 16;
     int shift = (internalBitDepth > 8) ? internalBitDepth - 9 : 0;
@@ -1795,6 +1826,7 @@ void IntraPrediction::xGetLMParameters(const PredictionUnit &pu, const Component
       a       = (((maxLuma[1] - minLuma[1]) * g_aiLMDivTableHigh[diff - 1] + div + add) >> shift);
     }
     b = minLuma[1] - ((a * minLuma[0]) >> iShift);
+#endif
   }
   else
   {

source/Lib/CommonLib/Rom.cpp

@@ -180,6 +180,7 @@ public:
     return rtn;
   }
 };
+#if !JVET_M0064_CCLM_SIMPLIFICATION
 int g_aiLMDivTableLow[] = {
   0,     0,     21845, 0,     13107, 43690, 18724, 0,     50972, 39321, 53620, 21845, 15123, 9362,  4369,  0,     3855,
   58254, 17246, 52428, 49932, 59578, 25644, 43690, 28835, 40329, 16990, 37449, 56496, 34952, 4228,  0,     61564, 34695,
@@ -244,6 +245,7 @@ int g_aiLMDivTableHigh[] = {
   134,   134,   134,   133,   133,   133,   132,  132,  132,  132,  131,  131,  131,  131,  130,  130,  130,  130,
   129,   129,   129,   129,   128,   128,   128,  128,
 };
+#endif
 const int8_t g_GbiLog2WeightBase = 3;
 const int8_t g_GbiWeightBase = (1 << g_GbiLog2WeightBase);
 const int8_t g_GbiWeights[GBI_NUM] = { -2, 3, 4, 5, 10 };

source/Lib/CommonLib/Rom.h

@@ -214,8 +214,10 @@ extern const uint32_t g_scalingListSizeX[SCALING_LIST_SIZE_NUM];
 
 extern MsgLevel g_verbosity;
 
+#if !JVET_M0064_CCLM_SIMPLIFICATION
 extern int g_aiLMDivTableLow[];
 extern int g_aiLMDivTableHigh[];
+#endif
 
 extern const int g_aiNonLMPosThrs[];
 

source/Lib/CommonLib/TypeDef.h

@@ -50,6 +50,8 @@
 #include <assert.h>
 #include <cassert>
 
+#define JVET_M0064_CCLM_SIMPLIFICATION                    1
+
 #define JVET_M0479_18BITS_MV_CLIP                         1
 
 #define JVET_M0502_PRED_MODE_CTX                          1